I just picked this up a week and a half ago and it's everything I'd always heard it was, and more. Phenomenal lens in every respect. I paid $800 for mine, all that was missing was the box and manual. Lens was in almost perfect condition, with one little blemish you'd have to look for. I can't understand why I only paid $800 for it, it's incredible. I had the Sigma 70-200/2.8 that I thought was amazing until I acquired this L. In fairness, the Sigma was an awesome lens, but I didn't have the Canon to compare it to.
The pictures this produces on my 1D have a sharpness and a feel to them I haven't seen before. The colors are so warm and true...
Completely and totally recommended, especially if you can get one at a price comparable to what I paid. It just makes it that much better!

Virtually nothing. High ISO noise is overblown (usually by those have never owned one of these AMAZING cameras), and Canon batteries don't give you much life (easily rectified by the purchase of 2200 mA 3rd party batteries). Banding does exist on earlier production models, but only really if underexposed and pushed

I've had this camera so long, I don't know why I haven't reviewed it before now. There is just something about this camera as a whole that's indescribable. The images are magical (with even fairly decent glass). I had to sell my first one for financial reasons, then scrimped and saved to buy a 1D Mark II in time for my daughter's birth. I had the MKII long enough to realize that I just HAD to have the original 1Dinosaur again. I would have been almost completely happy with the MK II, had I never owned the Classic. So I swapped the MK II (here on the awesome FM) for a mint 1D + cash and haven't looked back *in the least*.
As noted in the Cons section, high ISO noise isn't a problem at all (even at ASA 3200) as long as the pic is exposed properly. It's been said many times in other reviews that it truly does look like film grain.
The file sizes save you twice the storage space of the MK II (or 20D, for that matter. I tried one of them as well and went RUNNING back to my 1D!!!), and that CCD does things that Canon's CMOS can't even think about (granted, the CMOS + DIGIC II have their own positive attributes, just not enough to win me over). The weaker AA filter gives positively unrivalled sharpness, and I have yet to run into any moire issues. Their are PS actions for interpolating the files for printing at just about whatever size you want, and they hold up beautifully.
One "warning" if you want to call it that - the 1 Series aren't small, light cameras. They're built to take punishment, so they're not small or light, but everything else I've owned have felt like toys in comparison. I love the build of these beasts!
Also, if you shoot .jpgs out of the camera (they do look gorgeous!), you will want to download the custom curve that removes the green cast. It does exist.
If you're on the fence about this camera, I can't stress it enough - TRY IT. I've had this model for years, and there simply isn't ANYTHING out there that makes me want to switch. I've had the DRebel, XT, 20D and the 1D2, and this one is "just right".
Sorry for being overly verbose (actually, no I'm not. Don't read the review if you don't want to), but I really didn't even touch on everything I could have. Suffice it to say that only the 1DsII gets a 9.7 rating. Everything else is just *close*...
I love this camera! :D